Bip39. The passphrase is just not picked through the predefined list of 2048 words – it may be any word or phrase you end up picking. By using a passphrase, you add an additional layer of safety in your wallet, preserving your funds even though your seed phrase is compromised. https://socialrator.com/story9373466/bip39-https-linktr-ee-bip39-bip39-words-fundamentals-explained